Proton exchange membrane water electrolyzer membrane electrode assembly

ABSTRACT

Method for forming a membrane electrode assembly, include for example, providing a first layer membrane, a second layer membrane, an anode electrode, and a cathode electrode. The first layer membrane has a first thickness, the second layer membrane has a thickness less than the first thickness, and the second layer membrane contains a catalyst content that is greater than a catalyst content in the first layer membrane. The first layer membrane, the second layer membrane, the anode electrode, and the cathode electrode are formed into a membrane electrode assembly (MEA) comprising an exchange membrane having an interface between the first layer membrane and the second layer membrane. In some embodiments, may include a first and second lamination process, a single laminating process, a roll-to-roll process, and/or a casting process.

CLAIM TO PRIORITY

This application claims priority benefit of U.S. provisional patentapplication No. 63/144,539 filed Feb. 2, 2021, entitled “Proton ExchangeMembrane Water Electrolyzer Membrane Electrode Assembly,” whichapplication is incorporated herein by reference in its entirety.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to commonly assigned, patent application no.______, filed on ______ entitled “Proton Exchange Membrane WaterElectrolyzer Membrane Electrode Assembly” (atty. dock. no. 1404.313B),which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to proton exchange membranewater electrolyzer membrane electrode assemblies (MEAs), and moreparticularly, fabrication of membranes for water electrolyzer membraneelectrode assemblies (MEAs).

BACKGROUND

The utilization of renewable energy has driven substantial investmentsinto water electrolysis technologies. It is estimated that the waterelectrolysis market could increase to 300 GW over the next two decades,and power-to-gas is poised to become a multi-billion-dollar market foron-site electrolyzer systems over the next decade.

A proton exchange membrane (PEM) electrolysis cell is a device whichproduces hydrogen and oxygen gas by using DC electricity toelectrochemically split water. A PEM cell contains an “active area” inwhich the presence of catalyst permits the reactions to take place. Inthe electrolysis cell, the water enters the anode and is split intoprotons, electrons, and oxygen gas. The protons are conducted throughthe membrane while the electrons pass through the electrical circuit. Atthe cathode, the protons and electrons recombine to form hydrogen gas.The electrolysis half-reactions are shown below.

2H₂O→4H⁺+4e ⁻+O₂

4H⁺+4e ⁻→2H₂

FIG. 1 illustrates a prior art wet process 10 for forming a wet membranefor a proton exchange membrane water electrolyzer membrane electrodeassembly. In the wet process, at block 12 an ionomer membrane (e.g.,Nafion N115) is received, and at block 14 the ionomer membrane is boiledfor one hour for hydration. At block 16, the hydrated membrane then goesthrough a multiple-step platinization process for crossover mitigationpurposes that takes approximately five days in total. At block 18, afterthe membrane platinization, the membrane is then exchanged back to theH⁺ form, and at block 20, rinsed and boiled in deionized water. Once themembrane is processed, it has to be kept wet during the cell assemblyprocess.

Klose et al. developed an 8 mil tri-layer membrane using a spray coatingcontaining Pt to form an interlayer between NR212 and N115 membranes. C.Klose et al 2018, Membrane Interlayer with Pt Recombination Particlesfor Reduction of the Anodic Hydrogen Content in PEM Water Electrolysis,J. Electrochem. Soc. 165 F1271.

SUMMARY

Shortcomings of the prior art are overcome and additional advantages areprovided through the provision of a method for forming a membraneelectrode assembly, which include for example, providing a first layermembrane, a second layer membrane, an anode electrode and a cathodeelectrode. The first layer membrane has a first thickness, the secondlayer membrane has a thickness less than the first thickness, and thesecond layer membrane contains a catalyst content that is greater than acatalyst content in the first layer membrane. The first layer membrane,the second layer membrane, the anode electrode, and the cathodeelectrode are formed into a membrane electrode assembly (MEA) comprisingan exchange membrane having an interface between the first layermembrane and the second layer membrane.

In some embodiments, the method may include for example, the formingincluding first laminating the first layer membrane to the second layermembrane to form the exchange membrane, and second laminating the anodeelectrode to a first side of the exchange membrane, and the cathodeelectrode to a second side of the exchange membrane to form the membraneelectrode assembly (MEA).

In some embodiments, the method may include the forming includingproviding a layup having the first layer membrane, the second layermembrane on the first layer membrane to define the interface between thefirst layer membrane and the second layer membrane, the cathodeelectrode disposed on an outside of the first layer membrane, and theanode electrode on an outside of the second layer membrane, andlaminating the layup of the cathode electrode, the first layer membrane,the second layer membrane, and the anode layer to form the membraneelectrode assembly (MEA) having the bi-layer membrane.

In another embodiment a method includes, for example, providing a firstlayer membrane having a first thickness, providing a second layermembrane having a thickness less than the first thickness, and thesecond layer membrane containing a catalyst, the catalyst content in thesecond layer membrane being greater than a catalyst content in the firstlayer membrane, and forming the first layer membrane and the secondlayer membrane into an exchange membrane having an interface between thefirst layer membrane and the second layer membrane.

In another embodiment, a method for electrolyzing water may include, forexample, providing the a above membrane electrode assemblies (MEAs), andapplying a voltage potential across the cathode electrode and the anodeelectrode to produce hydrogen.

In another embodiment, a method for electrolyzing water may include, forexample, providing a membrane electrode assembly (MEA) having anexchange membrane with a first layer membrane having a first thickness,a second layer membrane having a thickness less than the firstthickness, a catalyst content in the second layer membrane is greaterthan a catalyst content in the first layer membrane, an interfacebetween the first layer membrane and the second layer membrane, an anodeelectrode, and a cathode electrode, and applying an electrical potentialacross the cathode electrode and the anode electrode to producehydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the disclosure is particularlypointed out and distinctly claimed in the concluding portion of thespecification. The disclosure, however, may best be understood byreference to the following detailed description of various embodimentsand the accompanying drawings in which:

FIG. 1 is a flowchart of a prior art wet processing method for forming acatalyst membrane for use in a membrane electrode assembly.

FIG. 2 is a membrane electrode assembly employing an exchange membrane,according to an embodiment of the present disclosure;

FIG. 3 is a flowchart for forming an exchange membrane, according to anembodiment of the present disclosure;

FIG. 4 is a diagrammatic illustration of a process for forming a layermembrane having a catalyst on a substrate, according to an embodiment ofthe present disclosure;

FIG. 5 is a diagrammatic illustration of a roll-to-roll process forforming a layer membrane having a catalyst on a substrate, according toan embodiment of the present disclosure

FIG. 6 is a diagrammatic illustration of a roll-to-roll process forforming a bi-layer membrane lamination, according to an embodiment ofthe present disclosure;

FIG. 7 is a diagrammatic illustration of a roll-to-roll process forforming a membrane electrode assembly employing a two-step laminationprocess, according to an embodiment of the present disclosure;

FIG. 8 is a flowchart for forming a membrane electrode assemblyemploying a bi-layer membrane lamination process, according to anembodiment of the present disclosure;

FIG. 9 is a flowchart for forming membrane electrode assembly employinga one-step lamination process, according to an embodiment of the presentdisclosure;

FIG. 10 is a flowchart for forming a recombination layer coated anodedecal, according to an embodiment of the present disclosure;

FIG. 11 is a diagrammatic illustration of a roll-to-roll process forforming a membrane electrode assembly employing a one-step laminationprocess with the membrane electrode assembly having a bi-layer membrane,according to an embodiment of the present disclosure;

FIG. 12 is a flowchart for forming a membrane electrode assembly with aone-step lamination process having a bi-layer membrane, according to anembodiment of the present disclosure;

FIG. 13 is a graph of polarization curves of a traditional wet-process,and MEAs made from the two dry-process;

FIG. 14 is a prior art graph of the theoretical calculation of theoptimized recombination layer thickness under different hydrogenbackpressure;

FIG. 15 is a prior art pie chart of a PEM electrolyzer system capitalcost; and

FIG. 16 is a graph of prior art PEM electrolyzer efficiency as afunction of current density, operation temperature and membranethickness.

DETAILED DESCRIPTION

The present disclosure is directed to an exchange membranes and membraneelectrode assemblies (MEAs) employing such exchange membranes. Forexample, the exchange membranes may be bi-layer electrolyzer membranesfor a water electrolyzer membrane electrode assemblies (MEAs) whereby arecombination catalyst such as platinum (Pt) is favorably deposited onone side of the exchange membrane structures, as an example on only oneside, preferably near the electrode with the low-pressure side of theelectrolyzer. It will be appreciated that the exchanges membrane mayinclude solely a bi-layer exchanges membrane or a bi-layer membrane withadditional membrane layers. For example, in an electrolyzer with highpressure hydrogen and low pressure oxygen, hydrogen will permeate morequickly, and therefore the platinum (Pt) recombination catalyst ispreferable near the oxygen electrode. Similarly, in a high-pressureoxygen configuration the Pt/ionomer layer will preferably be closer tothe hydrogen (cathode) side of the membrane electrode assembly. Alsodisclosed are methods of manufacturing the exchange membranes andmembrane electrode assembly (MEA) structures.

As will be appreciated from the present description, the techniques ofthe present disclosure for forming, for example, bi-layer membranes havedemonstrated the capability of dry processes for PEM electrolyzer MEAfabrication without sacrificing performance compared to wet processing.The dry processes may save on total capital cost for PEM electrolyzerfabrication by replacing labor-intensive and time-consuming wet membraneplatinization process with simple mitigation layer casting and drylamination processes. In addition to the labor cost, the bi-layermembrane design will also save on material cost. The amount of platinumrecombination catalyst in the membrane may be substantially reduced byapplying the catalyst in a 1.5 mil layer of the membrane close to theanode catalyst layer instead of inefficiently distributing therecombination catalyst through the whole membrane.

As described below, in some embodiments, a thin layer of platinum (Pt)nanoparticles may be laminated on top of the Nafion membrane to replacethe traditional platinum (Pt) doping in the whole membrane. Suchprocesses may reduce the amount of Pt used in the membrane (for example,about 1 wt. % to about 5% wt. %), but may also improve the durabilityand reliable of the PEMWE devices. In addition, by avoiding a wetassembling process, the process may be easier to be integrated into aroll to roll (R2R) process for MEA fabrication, which may increaseefficiency and save on labor involved.

FIG. 2 illustrates a membrane electrode assembly (MEA) 100 employing anexchange membrane 110, according to an embodiment of the presentdisclosure. For example, exchange membrane 110 may include a first layermembrane 120, a second layer membrane 140, a cathode electrode 130, anda cathode electrode 150. First layer membrane 120 has a first thickness,second layer membrane 140 has a thickness less than the first thickness,and second layer membrane 140 contains a catalyst content that isgreater than a catalyst content in first layer membrane 120. First layermembrane 120, second layer membrane 140, cathode electrode 130, andanode electrode 1510 are formed into membrane electrode assembly 100(MEA) having an exchange membrane 110 with an interface 115 betweenfirst layer membrane 120 and second layer membrane 140. As describedbelow, exchange membrane may have two different layer membranes, andformed by the fabrication process described below or other suitableprocesses. It will be appreciated that the exchange member may have morethan two distinct layers wherein two of the layers provide an interfacebetween the layers having differing catalyst content such as secondlayer member having less catalyst or on catalyst compared to the firstlayer membrane having a catalyst or greater catalyst content.

As will be appreciated, the present configuration of the bi-layerexchange membrane in an MEA electrolyzer may include avoiding the needfor hydrogen pumps and/or mitigating the H2 crossover to reduce safetyhazard, and be desirable for high pressure large scale waterelectrolyzer cells. Hydrogen is often purified and/or compressed so thatit can be stored for usage. Hydrogen pumps have been used for hydrogenpurification and/or compression of hydrogen rich gas. Currently, highpressure storage is required to improve the energy density of hydrogenfuel. It is more efficient to directly pressurize the H2 from theelectrolysis process compared to using downstream mechanicalcompressors. However, the high differential pressure in electrolyzercells introduces an H2 crossover issue due to the increased likelihoodof H2 permeating the membrane and combining with O2 in the cathode. Onecommon approach for the H2 crossover mitigation is the dispersion ofrecombination catalyst (such as platinum) throughout the membrane. Thismaterial serves to catalyze the reaction between crossover-H2 with O2 onsurface of the cathode side of the membrane. However, when scaled up thelong processing and material cost of platinum catalyst used in themembrane increases labor and material cost which prevents currentmanufacturing process to meet the supply, cost and timeline of 1 MWstack orders.

With reference to FIG. 3, FIG. 3 illustrates a method 200 employing amembrane lamination approach, according to an embodiment of the presentdisclosure. In this illustrated embodiment, method 200 includes, forexample, in block 202 platinum (Pt) black material is incorporated in anionomer containing ink (EG Nafion D2021) to form a uniform dispersion.In one example, a uniform platinum (Pt) doped ionomer dispersion mayinclude 160 mg of Pt black, 10.1 mg of cerium hydroxide and 80 g ofNAFION D2021 ionomer that is balled milled in a plastic container usingmixing media. The dispersion is mixed for two days before it is ready tocast.

At block 204 the dispersion is cast into a thin membrane on a carriersubstrate to form the Pt/ionomer layer. For example, the dispersion maybe then coated on a substrate such as polyimide (Kapton) film such as aroll-to-roll process as described below.

At 206, the Pt/ionomer layer is then laminated to a membrane (e.g.,NAFION 212) that does not have platinum (Pt) incorporated therein. Forexample, the Pt/ionomer layered decal is then laminated with NAFIONNR212 membrane in a hot press at 320 degrees F. (Fahrenheit) for 3minutes to form a bi-layer membrane with a thickness approximately 3.5mil.

At 208, the by-layer membrane is ready for dry lamination to electrodes.For example, cathode and anode electrodes may then be laminated to theprepared bi-layer membrane to form a membrane electrode assembly (MEA).For example, cathode and anode electrodes may be then laminated on theNAFION NR212 side and the Pt/ionomer layer side of the bi-layermembrane, respectively, using a similar technique as the membranelamination process, e.g., in a hot press at 320 degrees F. (Fahrenheit)for 3 minutes.

FIG. 4 diagrammatically illustrates a process 220 for casting thedispersion into a thin membrane on a carrier substrate to form aPt/ionomer layer, according to an embodiment of the present disclosure.For example, a depositor 230 may include a controllable flow rate and acontrollable gap so that the depositor such as an injector or extrudermay continuously deposit a slurry layer 232 onto a moving substrate 234.The slurry 320 may include the ionomer with a catalyst such as platinum(Pt). The slurry may be deposed having a thickness of 1-1.5 mil, and thesubstrate may be polyimide acker film such as a 3 mil Kapton substrate,or a polyimide.

FIG. 5 illustrates a roll-to-roll process 250, according to anembodiment of the present disclosure. In this illustrated embodiment, adepositor 260 such as an injector or extruder may continuously deposit aslurry catalyst/ionomer layer 265 onto a moving first substrate 275,which moving substrate is unwound from a roll 270. The slurry 265 mayinclude the ionomer with a catalyst such as platinum (Pt) and radicalscavenger such as cerium hydroxide that may mitigate degradation of themembrane. The slurry may be deposed having a thickness of 1-1.5 mil, andthe substrate may be a 3 mil Kapton substrate. The slurry may be curedor partially cured by [passing through a drying step such as passingthrough a heater or furnace 280. The dry catalyst/ionomer layer 265 andsubstrate may be wound onto a roll 290.

FIG. 6 diagrammatically illustrates a process 300 for forming alaminated bi-layer exchange membrane, according to an embodiment of thepresent disclosure. As illustrated in FIG. 6, an ionomer layer with acatalyst may be formed in a roll-to-roll process, and the bi-layermembrane may be formed in a lamination process. For example, a depositor310 such as an injector or extruder may continuously deposit a slurrylayer 320 onto a moving substrate 330. The slurry 320 may include theionomer with a catalyst such as platinum (Pt). The slurry may be deposedhaving a thickness of about 1 mil, and the substrate may be a 3 milKapton substrate.

After the slurry is cured or partially cured such as passing through adryer of furnace, the ionomer layer 320 and substrate 330 may be die cutand formed into a die cut structure 350 or otherwise processed to adesired shape or size. For example, die cut structure 350 may be sizedbased on the size of the desired membrane electrode assembly (MEA) to befabricated. In some embodiments, then die cut structure 350 may have asize such as a 50 cm² or 1200 cm².

A die cut second structure 380 may include a membrane layer 360, forexample, not having a catalyst and a second substrate 370. Membranelayer 360 may be a 2 mil NR212 membrane, and second substrate 370 may bea NR212 backer such as a 3 mil mylar layer. Die cut structure 350 anddie cut structure 380 may be laminated together in a hot press.

FIG. 7 illustrates a roll-to-roll process 400 for forming a MEA, forexample, having a two-step lamination process, according to anembodiment of the present disclosure.

As illustrated in FIG. 7, a depositor 410 such as an injector orextruder may continuously deposit a slurry catalyst/ionomer layer 420onto a moving first substrate 430, which moving substrate is unwoundfrom a roll 432. The slurry 420 may include the ionomer with a catalystsuch as platinum (Pt) and radical scavenger such as cerium hydroxide.The slurry may be deposed having a thickness of about 1 mil, and thesubstrate may be a 3 mil Kapton substrate. After the slurry is cured orpartially cured such as by passing through a heater, furnace or dryer415, a membrane layer 440, for example, not having a catalyst anddisposed on a backer on one side is unwound from a roll 442 anddeposited on the cured or partially cured slurry layer 420. Membranelayer 440 may be a 2 mil N212 membrane.

The layers are assembled and pass through a first hot press 460 having,for example, a first heated roller 462 and a second heated roller 464.First substrate 430 is removed and wound onto a roller 474 and thesubstrate on NR212 membrane 440 is removed and wound on a roller 472. Ananode electrode 480 is unwound from a roll 482 and deposited on ordeposited adjacent to catalyst layer 420. A cathode electrode 490 isunwound from a roll 492 and deposited on or disposed adjacent tomembrane 440. Anode electrode 480, catalyst layer 420, membrane layer440 without a catalyst, and cathode electrode 490 pass through a secondhot press 466, for example, having a first heated roller 467 and asecond heated roller 468 to form a laminated MEA.

FIG. 8 illustrates a method 500 for forming a membrane electrodeassembly, according to an embodiment of the present disclosure. In thisillustrated embodiment, method 500 includes, for example, at 510,providing a first layer, at 520 providing a second layer containing acatalyst, at 530 providing an anode electrode, at 540 providing acathode electrode, and at 550 forming the first layer, the second layercontaining a catalyst, the anode electrode, and the cathode electrodeinto a membrane electrode assembly (MEA), wherein the first layer andthe second layer form, and wherein a catalyst content in the secondlayer is greater than a catalyst content in the first layer.

FIG. 9 illustrates a method 600 for forming a mitigation layer coatedanode, according to an embodiment of the present disclosure. Thisexemplary approach may facilitate the use of only one high temperaturelamination step during the fabrication of the membrane electrodeassembly (MEA). The approach may simplify a membrane electrode assembly(MEA) fabrication process and reduce the time of high temperaturelamination process which may cause mechanical and chemical degradationof the membrane, compared to the methods described and illustrated inFIGS. 4-8.

In this illustrated embodiment, as shown in FIG. 9, a method 600includes in block 602 preparing a platinum (Pt) doped ionomerdispersion. The preparation may be the same as the platinum (Pt) dopedionomer dispersion prepared in block 202 (FIG. 3) described above. Inblock 604, the as-prepared platinum (Pt) doped ionomer dispersion isthen cast on an anode decal. In this embodiment, the anode decal isanode catalyst layer plus a substrate liner. Multiple passes may berequired until a 1.5 mil membrane thickness is achieved. The 1.5 millayer may have about 0.01 to about 0.5 mg(Pt)/cm² PGM loading. In block606, the mitigation layer coated anode is ready for dry lamination. Forexample, a commercial cathode or catalyst layer coated gas diffusionmedia may be then laminated via hot pressing on to both of a Nafion N212membrane at 320 degrees F. for three minutes. The mitigation layercoated anode approach may potentially yield additional cost savings onthe NAFION ionomer and recombination catalyst since the mitigation isonly applied on the active area instead of being on the entire membranearea, and a single lamination step is required.

FIG. 10 diagrammatically illustrates a process 700 for forming arecombination layer coated anode decal, according to an embodiment ofthe present disclosure. As illustrated in FIG. 10, an anode catalystlayer 720 may be formed in a roll-to-roll process. For example, adepositor 710 such as an injector or extruder may continuously depositanode catalyst layer 720 onto a moving substrate 730. The depositedanode catalyst layer and substrate may pass through a dryer.

An ionomer layer with a catalyst may be formed in a roll-to-rollprocess. For example, a depositor 750 such as an injector or extrudermay continuously deposit a slurry layer 760 onto a moving anode catalystlayer electrode 720 disposed and supported on a substrate 730. Theslurry 760 may include the ionomer with a catalyst such as platinum (Pt)and radical scavenger such as Cerium hydroxide. The slurry may bedeposed having a thickness of about 1-1.5 mil, and the substrate may bea 3 mil ethylene tetrafluoroethylene (ETFE), a fluorine-based plastic.The deposited ionomer layer with a catalyst may pass through a dryer.

The configured structure 770, e.g., formed recombination layer coatedanode decal, may be die cut to a desired size. A membrane layer withouta catalyst and a cathode electrode (not shown) may be disposed orotherwise placed on structure 700. A single lamination process, e.g.,hot pressing, may be employed to form the membrane electrode assembly(MEA). In other embodiments, the membrane may be disposed on structure770 in a roll-to-roll process. The membrane layer may be a 2 mil N212membrane.

FIG. 11 illustrates a roll-to-roll process 800 for forming a membraneelectrode assembly (MEA), for example, having a one-step laminationprocess, according to an embodiment of the present disclosure.

As illustrated in FIG. 11, a depositor 810 such as an injector orextruder may continuously deposit an anode catalyst layer 820 onto amoving substrate 830. The deposited anode catalyst layer and substratemay pass through a dryer 815. A depositor 850 such as an injector orextruder may continuously deposit a slurry catalyst layer 860 onto amoving cathode electrode 820 and first substrate 830, which substrate isunwound from a roll 832, respectively. The slurry 860 may include theionomer with a catalyst such as platinum (Pt) and radical scavenger suchas cerium hydroxide. The slurry may be deposed having a thickness ofabout 1-1.5 mil, and substrate 830 may be a 3 mil ETFE substrate. Thedeposited slurry 860 may pass through a dryer 855. After the slurry iscured or partially cured, a membrane layer 840 not having a catalystwith a backer or second substrate on one side is unwound from a roll 842and deposited on the cured or partially cured slurry layer 860, thebacker being removed on a roll 844. Membrane layer 840 may be a 2 milN212 membrane, and the second substrate or backing layer may be a 3 milmylar layer. A cathode electrode 880 is unwound from a roll 882 anddeposited on or deposited adjacent to membrane 840. The layers areassembled and may pass through a hot press 865 having, for example, afirst heated roller 861 and a second heated roller 863 to form alaminated structure for an MEA.

In some embodiments, the dispersion may be cast into a thin membrane ona carrier substrate to form the Pt/ionomer layer. For example, thedispersion may be then coated on a substrate such as polyimide (Kapton)film using a doctor blade film applicator. Multiple layers of castingare performed as needed until, for example, a 1.5 mil of membranethickness is achieved.

FIG. 12 illustrates a method 900 for forming a membrane electrodeassembly, according to an embodiment of the present disclosure. In thisillustrated embodiment, method 900 includes, for example, at 910providing a first layer, at 920 providing a second layer containing acatalyst, at 930 providing an anode electrode, at 940 providing acathode electrode, and at 950 forming the first layer, the second layercontaining a catalyst, the anode electrode, and the cathode electrodeinto a membrane electrode assembly (MEA), wherein the first layer andthe second layer form, and wherein a catalyst content in the secondlayer is greater than a catalyst content in the first layer.

FIG. 13 illustrates test results of the traditional wet-built MEA usingN115 membrane and the dry-built membrane electrode assemblies (MEAs)prepared from both approaches having a 3.5 mil thick bi-layer membrane.It was observed that the MEAs using the bi-layer membrane made frommembrane lamination approach has a similar performance compared to aconventional wet-process MEA, which indicates the feasibility andpotential for the dry-built PEM electrolyzer MEAs.

It will be appreciated that the technique of the present disclosureovercomes the problems with the spray coating approach of Klose et al.For example, the spray coating approach of Klose et al. is neithereasily controlled nor well suitable for large scale manufacturing. Inaddition, the spray coating approach is also limited by the low Ptutilization in the middle Pt interlayer. Hydrogen molecule has a muchhigher diffusivity compared to oxygen. Under high back pressure,hydrogen will travel much faster than oxygen in the membrane, thus therecombination will happen at the interface of the membrane and anodecatalyst layer.

The literature has described the theoretical calculation of theoptimized recombination layer thickness under different hydrogenbackpressure. FIG. 14 illustrates an ideal dimensionless position of arecombination interlayer (hydrogen flux twice the amount of oxygen flux)versus the cathode pressure. For anode pressure of 1 bar, 6 bar, 10 bar,20 bar, and balanced pressure conditions. Calculations are for 80degrees Celsius.

With higher hydrogen backpressure, the location of the recombinationlayer is disposed closer to the surface of electrolyzer anode. in thepresent disclosure with the condition of a 40 bar cathode and a 3 baranode, the recombination layer may be within 10% thickness of the wholemembrane thickness on the anode side. Another benefit of the presentdisclosure is the flexibility of tuning the thickness of therecombination to better accommodate different hydrogen backpressureoperation. The recombination may be disposed at the membrane/anodeinterface.

FIG. 15 illustrates a cost breakdown for a prior art PEM electrolyzersystem capital cost. Colella, W. G., James, B. D., Moton, J. M., Saur,G. and Ramsden, T., 2014, February, Techno-economic analysis of PEMelectrolysis for hydrogen production, in Electrolytic hydrogenproduction workshop, NREL, Golden, Colo. (Vol. 27). As observed, thestack is the major component of the overall capital cost in a PEMelectrolyzer system. The membrane electrode assembly (MEA) is one of themajor components which comprises greater than 25 percent of the stackcost.

As will be appreciated from the present disclosure, a fully dry membraneprocess may be desirable by reducing the membrane processing time andlabor cost, compared with the wet membrane process. In addition, the drymembrane process can maintain the mechanical strength of the membranewhile eliminating the dimensional change during the membrane processing.By avoiding sacrificing mechanical strength, using a thinner membranebecomes possible. In order to distribute the recombination catalystlayer only in the region where H₂/O₂ recombination reaction takes place,a separate recombination layer which contains uniformly distributed Ptnanoparticles may significantly reduce the H₂ crossover to reduce thesafety hazard. Compared to the current state-of-art technique, in whichthe whole membrane is platinized, the recombination layer is moreefficient and economical by reducing the amount of Pt in the membrane.In addition, the dry-built bi-layer membrane retains all the advantagesof wet-built membrane while maintaining the mechanical strength of themembrane reducing the labor cost at the same time. Moreover, the dryprocess allows for thinner membranes as mechanical handling is improved,and membranes installed dry will expand in the thickness direction,compared to current state-of-the-art PEM electrolysis with a 0.005-0.007inch (5-7 mil) membrane operating at 70 degrees C. and 3000 mA/cm2, a0.003 inch (3 mil) membrane at 95 degrees C. can operate at twice thecurrent density, thus halving CapEx of the electrolyzer stacks, as shownin FIG. 16. In an expensive electricity environment, one may be able tohold the current density constant while using 12% less energy at thestack level.

From the present description, it will be appreciated that the dryprocessing methods of the present disclosure provides advantages overconventional wet processing processes. For example, wet processing is alaborious and time-consuming process is not suitable for high throughputand multi-MW electrolyzer manufacturing. Once wet, the membranes must bekept and assembled wet. In addition, the wet process of the membranetakes about a large amount of labor cost for the electrolyzermanufacturing. As mentioned, the platinization of the membrane usingconventional wet processing approach generally takes long time, which istime consuming and introduces huge amount of labor cost. In addition tothe long processing time and high labor cost, the platinization processdisperses excess platinum particles indiscriminately through the entiremembrane thickness, rather than where is it most effective. Consideringthe higher diffusion rates of H₂ and O₂, and much higher H₂ pressure,only the Pt particles closer to the anode side of the membrane areexpected to be active in reducing crossover of H₂ through recombination;therefore, the particles in other locations are inactive and only serveto add unnecessary cost. Moreover, the complicated wet process alsocompromises the mechanical strength of the membrane. This is anotherreason that thicker membranes are preferred in PEMWEs. Thus, it will beappreciated from the present disclosure that by replacing thetraditional wet-membrane process with a dry-membrane process using thetechniques of the present disclosure described and illustrated, thematerial and labor cost associated with MW-scale electrolyzermanufacturing may be reduced, thus enabling the viable penetration andadoption of MW electrolyzers in the renewable energy storage market.

The present disclosure overcomes the drawbacks of the Klose et al. 8 miltri layer membrane, which drawbacks include 1) membrane being too thickwhich impacts the efficiency of the electrolyzer dramatically, 2) sprayand lamination process to produce the “tri-layer membrane” is timeconsuming and not valuable for mass production, and 3) the location ofthe recombination is in the middle of two membranes, which is not easyto tune the location of the layer.

Benefits of the present disclosure over the Klose et al. 8 mil tri layermembrane include 1) the bilayer membrane containing a 1 milrecombination layer plus NR212 membrane for in some embodiments totals a3 mil thickness and allows for an efficient electrolyzer, 2) the wholeprocess can be done in roll-to-roll that is fully automatic and suitablefor mass production, and 3) the recombination layer in the presentdisclosure is located on the anode side of the membrane. By tuning thethickness of the recombination, it can be adapted to different hydrogenback pressure.

As may be recognized by those of ordinary skill in the art based on theteachings herein, numerous changes and modifications may be made to theabove-described and other embodiments of the present disclosure withoutdeparting from the scope of the disclosure. The components of the MEAsas disclosed in the specification, including the accompanying abstractand drawings, may be replaced by alternative component(s) or feature(s),such as those disclosed in another embodiment, which serve the same,equivalent or similar purpose as known by those skilled in the art toachieve the same, equivalent or similar results by such alternativecomponent(s) or feature(s) to provide a similar function for theintended purpose. In addition, the MEAs may include more or fewercomponents or features than the embodiments as described and illustratedherein. Accordingly, this detailed description of thecurrently-preferred embodiments is to be taken in an illustrative, asopposed to limiting of the disclosure.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has”, and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform of contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises,” “has,”“includes,” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises,” “has,” “includes,” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

The disclosure has been described with reference to the preferredembodiments. It will be understood that the embodiments described hereinare exemplary of a plurality of possible arrangements to provide thesame general features, characteristics, and general system operation.Modifications and alterations will occur to others upon a reading andunderstanding of the preceding detailed description. It is intended thatthe disclosure be construed as including all such modifications andalterations.

1. A method comprising: providing a first layer membrane having a firstthickness; providing a second layer membrane having a thickness lessthan the first thickness, and the second layer membrane containing acatalyst, the catalyst content in the second layer membrane beinggreater than a catalyst content in the first layer membrane; providingan anode electrode; providing a cathode electrode; and forming the firstlayer membrane, the second layer membrane, the anode electrode, and thecathode electrode into a membrane electrode assembly (MEA) comprising anexchange membrane having an interface between the first layer membraneand the second layer membrane.
 2. The method of claim 1 wherein theproviding the first layer membrane comprises providing the first layermembrane without a catalyst.
 3. The method of claim 1 wherein theexchange membrane comprises a bi-layer exchange membrane.
 4. The methodof claim 1 wherein the anode is disposed directly against the secondlayer.
 5. The method of claim 1 wherein the forming comprises: firstlaminating the first layer membrane to the second layer membrane to formthe exchange membrane; and second laminating the anode electrode to afirst side of the exchange membrane, and the cathode electrode to asecond side of the exchange membrane to form the membrane electrodeassembly (MEA).
 6. The method of claim 1 wherein the providing anddepositing comprises a roll-to-roll process of providing the secondlayer membrane comprising depositing a slurry on a moving substrate. 7.The method of claim 6 wherein: the first laminating comprises aroll-to-roll laminating process of the first layer membrane to thesecond layer membrane; and the second laminating comprises aroll-to-roll laminating process of the anode cathode and cathode anodeto the exchange membrane.
 8. The method of claim 1 wherein the formingcomprises: providing a layup comprising: the first layer membrane; thesecond layer membrane on the first layer membrane to define theinterface between the first layer membrane and the second layermembrane; the cathode electrode disposed on an outside of the firstlayer membrane; the anode electrode disposed on an outside of the secondlayer membrane; and laminating the layup of the cathode electrode, thefirst layer membrane, the second layer membrane, and the anode electrodeto form the membrane electrode assembly (MEA).
 9. The method of claim 8wherein the providing comprises a roll-to-roll process of providing thesecond layer membrane comprising depositing a slurry on a movingsubstrate.
 10. The method of claim 9 wherein: the laminating comprises asingle roll-to-roll laminating process of the layup.
 11. The method ofclaim 1 wherein providing the second layer comprises: casting a catalystdispersion on a substrate.
 12. The method of claim 11 wherein thecasting comprises 0.01-0.5 mgPt/cm² PGM.
 13. The method of claim 11wherein: the providing the second layer membrane comprises: providingthe catalyst dispersion; forming a first coating of the catalystdispersion on the substrate; and forming successive coatings on thefirst coating until a predetermined thickness of the first layermembrane is achieved.
 14. The method of claim 11 wherein the providing acatalyst dispersion comprises providing a catalyst dispersion comprisingplatinum (Pt) black, cerium hydroxide and NAFION ionomer.
 15. The methodof claim 11 wherein the providing a catalyst dispersion comprises: ballmilling platinum (Pt) black, cerium hydroxide and NAFION D2021 ionomerin the ratio of 160 mg of platinum (Pt) black, 10.1 mg of ceriumhydroxide and 80 g of NAFION D2020 ionomer with beads for two days. 16.The method of claim 1 wherein the laminate comprises 1 percent of thecatalyst by weight.
 17. The method of claim 1 wherein the providing thefirst layer membrane comprises providing a NAFION membrane and theproviding the second layer membrane comprises providing an ionomer layermembrane with a platinum (Pt) catalyst.
 18. The method of claim 1wherein the first layer membrane comprises a thickness of at least 1.5mil to 2 mil, and the second layer membrane comprises a thickness of1-1.5 mil.
 19. A method for electrolyzing water, the method comprising:providing the membrane electrode assembly (MEA) of claim 1; and applyinga voltage potential across the cathode electrode and the anode electrodeto produce hydrogen.
 20. A method for electrolyzing water, the methodcomprising: providing a membrane electrode assembly (MEA) comprising: anexchange membrane comprising: a first layer membrane having a firstthickness; a second layer membrane having a thickness less than thefirst thickness, a catalyst content in the second layer membrane isgreater than a catalyst content in the first layer membrane; aninterface between the first layer membrane and the second layermembrane; and an anode electrode; a cathode electrode; and applying anelectrical potential across the cathode electrode and the anodeelectrode to produce hydrogen.
 21. The method of claim 20 wherein: thefirst layer membrane comprises a layer membrane without a catalyst; andthe first layer membrane comprises a thickness of at least 1.5 mil to 2mil, and the second layer membrane comprises a thickness of 1-1.5 mil.22. The method of claim 20 wherein the exchange membrane comprises abi-layer exchange membrane.
 23. A method comprising: providing a firstlayer membrane having a first thickness; providing a second layermembrane having a thickness less than the first thickness, and thesecond layer membrane containing a catalyst, the catalyst content in thesecond layer membrane being greater than a catalyst content in the firstlayer membrane; and forming the first layer membrane and the secondlayer membrane into an exchange membrane having an interface between thefirst layer membrane and the second layer membrane.
 24. The method ofclaim 23 wherein: the providing the first layer membrane comprisesproviding the first layer membrane without a catalyst; and the exchangemembrane comprises a bi-layer exchange membrane.
 25. The method of claim23 wherein the forming comprises: hot pressing the first layer membraneto the second layer membrane to form the exchange membrane.
 26. Themethod of claim 23 wherein the providing the second layer membranecomprises a roll-to-roll process of depositing a slurry on a movingsubstrate.
 27. The method of claim 26 wherein the providing the firstlayer membrane comprises a roll-to-roll process of depositing a slurryon the second layer membrane.
 28. The method of claim 27 wherein theproviding a catalyst dispersion comprises providing a catalystdispersion comprising platinum (Pt) black, cerium hydroxide and NAFIONionomer.
 29. The method of claim 23 wherein the exchange membranecomprises 1 percent of the catalyst by weight.
 30. The method of claim23 wherein the first layer membrane comprises a thickness of 1.5 mil to2 mil, and the second layer membrane comprises a thickness of 1.5 mil.